This invention relates to a storage rack system. It relates more particularly to a rack assembly composed of one or more modular units or bays arranged in a straight row. Typically, a given system will comprise several such rows with aisles between them to enable stockpersons and order pickers to move between the rows and remove stock from the various bays for transfer to a central location to fill orders.
The rack assemblies can be arranged to store palletized loads or for live storage wherein the stock is supported on inclined gravity-flow shelves. In the latter case, restocking is done at the backs of the shelves and order picking from the fronts. The stock is kept fresh by the gravity feed of the stock toward the shelf fronts assuring storage on a first-in, first-out basis. Such rack assemblies also provide flexible warehousing of merchandise and assure a rack front-filled condition at all times with resultant maximum ease and minimum error of order picking, and simplification of stock control. An example of such a gravity-flow storage rack assembly is disclosed in U.S. Pat. No. 3,900,112.
There are a number of design criteria which such rack systems should meet, many of which are mutually antagonistic. More particularly, the system should be capable of providing both carton flow and pallet flow as well as reserve pallet storage in a wide variety of floor layouts, yet be composed of a minimum number of different parts. Also, the components of the system should be capable of being assembled relatively quickly without any special tools or equipment. Yet, when assembled, those components should combine and coact to create a rack structure or assembly which is capable of supporting heavy loads and which is very stable and able to withstand lateral forces exerted upon it by vehicles loading stores onto the rack shelves, horizontal conveyors supported by the assemblies, earth tremors, etc. Additionally, of course, positive engagements between the components of the rack system are essential to avoid accidental disconnection or dislocation of rack parts. Further economic considerations dictate that such maximum rigidity, ease of installation and economy of parts should be achieved using a minimum of assembly operations so that the storage rack system can be assembled on site by the purchaser of the system without any special training by following simple instructions.
While the rack assemblies of which we are aware, including the one disclosed in the aforementioned patent, satisfy some of the above criteria, they do not satisfy all of the mutually antagonistic requirements for present day rack systems, particularly those extending up two, three, four or more levels. In some cases, the vertical frames are not strong enough; in others, the connections between the various components of the system are not rigid or secure enough. For example, in the assembly described in the aforementioned patent, the vertical frames comprise channels having generally U-shaped cross sections making them somewhat susceptible to torsional-flexural buckling, particularly in the long lengths required for multiple level rack systems. Also, the horizontal frame members or sway braces are connected to the vertical frames by keyed connections that do not prevent all relative movement between the ends of the sway braces and the vertical frames. Consequently, those prior racks are not as rigid and sturdy as they might be, particularly when the racks extend up several levels.
There do exist rack assemblies which attempt to effect more secure connections or joints between the horizontal and vertical frame members of those assemblies with the objective of minimizing sway and maximizing the rigidity of the overall assembly. Examples of those racks are disclosed in U.S. Pat. Nos. 3,510,010; 3,871,525; 4,027,453 and 4,064,996. They employ special connectors at the ends of the horizontal frame members or braces which hook into the vertical frames with the objective of minimizing rotation of those members relative to the vertical frames and the chances of accidental disengagement of the connectors from the frames. However, even those structures are not as rigid and secure as they might be, particularly when installed in multiple level rack systems. The main reason for this is that the vertical frames are still composed of open channels and the connectors between the horizontal sway braces and those frames do not eliminate all relative motions between the braces and the frames. Moreover, when the racks are subjected to horizontal forces tending to cause the assembly to rack or sway, the connections between the sway braces and vertical frames sometimes cause the walls of the frame channels to bend and tear. Still further, in the prior racks, the mounting of the shelving to the vertical frames is not as convenient and adaptable as it might be.